Power Mesh Managing Method

ABSTRACT

The invention discloses a power mesh managing method utilized in an integrated circuit. The integrated circuit includes a standard cell and a standard-cell power supplying mesh corresponding to a first direction. The power mesh managing method includes: defining a power supplying network including a first plurality of power meshes growing along the first direction and a second plurality of power meshes growing along a second direction, and defining an assistant connecting network on a third metal layer, wherein the assistant connecting network includes a plurality of assistant connecting lines growing along the second direction, the first plurality of power meshes are formed on a first metal layer, the second plurality of power meshes on a second metal layer, the third metal layer is below the first metal layer, and the second metal layer is above the first metal layer.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The invention relates to a power mesh managing method and relatedintegrated circuit, particularly to a method for managing power mesh ofa standard cell and related integrated circuit.

(b) Description of the Related Art

As the APR (automatic placement and routing) tool not only helps acircuit designer placing circuit elements at the suitable locations inthe chip easily but also helps the circuit designer managing the powerrouting, the APR tool has become one of the indispensable tools for thecircuit designer.

Generally, the APR tool uses two types of blocks to manage circuitelements. One of them is the standard cell. As the name implies, thestandard cell is a type of standardized block having specific size andbuilt-in power managing method for managing some often-used standardcircuit elements, such as: flip-flops, logic gates, and the like. Then,the APR tool can neatly arrange a plurality of standard cells in thearea of a chip. The other one is the macro block. The macro block isdifferent from the standard cell. The macro block does not have fixedsize and is used to manage the circuits having specific functionsdesigned by the circuit designer, such as: SRAM, ADC, and so on.

However, the APR tool follows specific routing rules to appropriatelyarrange the macro block and the standard cell at the suitable locationsof the chip and to draw the power network. But, as the APR tool can onlyperform regular management, the details of the management still needsmanual adjustments by the designer. Therefore, the APR tool still needsto be improved.

Now please refer to FIG. 1 which shows a three-dimensional schematicdiagram illustrating the standard cell 100 and the standard cell powersupplying meshes 110, 120 managed by the APR tool according to the priorart. In general, as shown in FIG. 1, the standard cell power supplyingmeshes 110, 120 growing along the horizontal direction are placed alongeach side of the standard cell 100 according to the managing rule of thetraditional APR tool. The power supplying mesh 110 conducts the externalpower V_(DD) to the standard cell 100 while the power supplying mesh 120conducts the ground power V_(SS) to the standard cell 100.

Then, please refer to FIG. 2 which shows a three-dimensional schematicdiagram illustrating the standard cell 100, the standard-cell powersupplying meshes 110, 120, shown in FIG. 1, and the power supplyingnetwork 200 located above the standard cell 100. Please note that, forclarity, only three rows of standard cell 100 are shown in FIG. 2. But,in practical applications, there can be many more standard cells 100 inthe chip. As shown in FIG. 2, the lower part is the standard cell andthe standard cell power supplying meshes 110, 120 in FIG. 1 while theupper part is the power supplying network 200 managed by the APR toolaccording to the prior art. As shown in FIG. 2, the power supplyingnetwork 200 includes the horizontal power supplying mesh 210 and thevertical power supplying mesh 220. The vertical power supplying mesh 220and the horizontal power supplying mesh 210 are located in differentmetal layers. The vertical power supplying mesh 220 is positioned on thelayer above the horizontal power supplying mesh 210. The horizontalpower supplying mesh 210 is perpendicular to the vertical powersupplying mesh 220 to form a matrix. Besides, the horizontal powersupplying mesh 210 includes a plurality of mutually interlaced powerlines 211 and ground lines 212. The vertical power supplying mesh 220also includes a plurality of mutually interlaced power lines 221 andground lines 222.

Besides, the power lines 211, 221 must couple to the external power (notshown in the figure). The power lines 211, 221 couple to the abovementioned standard-cell power supplying mesh 110 through the via hole(“via”) and the via plug 230 for conducting the voltage V_(DD) that isprovided by the external power into the standard cell 100. On the otherhand, the ground lines 212, 222 also must couple to the ground voltageV_(SS). And, the ground lines 212, 222 couple to the standard-cell powersupplying mesh 120 through the via and the via plug 230 for conductingthe ground voltage into the standard cell 100. Please note that, forclarity, the via 230 between the horizontal power supplying mesh 210 andthe standard cell power supplying meshes 110, 120 is not shown in FIG.2. In general, the interlacing power lines, that are at the equalpotential, of the horizontal power supplying mesh 210 and the verticalpower supplying mesh 220 (such as: between 211 and 221 and between 221and 222) couple to each other at the overlapping area through the viaand the via plug. The via and the via plug to couple the power supplyingmeshes at the overlapping area are also not shown in FIG. 2, forclarity.

Please also note that, in order to conduct the external powerV_(DD)/ground voltage V_(SS) into the standard cell 100, the resistancebetween the external power and the standard cell 100 is generallyproperly designed to obtain better overall circuit performance. Theresistance between the external power and the standard cell 100 isdirectly related to the number of the vias and the via plugs. As is wellknown to the industry, due to the resistance shunting effect, the moreis the number of the vias/via plugs the more is the reduction of theresistance between the external power and the standard cell 100. Hence,the positions that can be allocated to the vias/via plugs becomecrucial. As mentioned before, the adjustable range of the resistancebecomes larger as there are more allocable positions for the vias/viaplugs. Therefore, in general, the routing rules of the APR tool areusually designed to place the vias and the via plugs, at the overlappingareas between the power supplying meshes 210/220 and the standard cellpower meshes 110/120 and at the overlapping areas between the powersupplying mesh 210 and the power supplying mesh 220 for coupling.However, such a design will cause some problems.

Now, please refer to FIG. 3 which shows a schematic diagram illustratingthe side view of the standard cell power meshes 110, 120 and thestandard-cell power supplying network 200 located in the upper layer. Asshown in FIG. 3, since the horizontal power supplying mesh 210 islocated in the layer below the vertical power supplying mesh 220, thehorizontal power supplying mesh 210 can be coupled to the standard-cellpower supplying meshes 110/120 by way of the via/via plug 230 withoutobstruction. Therefore, the above mentioned routing mechanism will notface too many problems. But, for the vertical power supplying mesh 220,since the vertical power supplying mesh 220 may be blocked by thehorizontal power supplying mesh 210 that may be positioned between thepower supplying mesh 220 located in the upper layer and thestandard-cell power supplying meshes 110, 120, the power supplying mesh220 located in the upper layer may not be able to couple to thestandard-cell power supplying meshes 110, 120 below by way of thevias/via plugs. Therefore, the positions for placing the vias/via plugsbecome limited. As shown in FIG. 3, the via/via plug 230 that is markedby “X” indicates that the via/via plug cannot be placed at thatlocation. That is, the via/via plug 230, that is supposed to couple thevertical power lines 221/222 in the upper layer to the standard cellpower meshes 110/120 in the lower layer, is blocked by the horizontalpower supplying mesh 210 and cannot be provided.

Besides, the above mentioned structure has another problem. In additionto the drawback that the horizontal power supplying mesh 210 blocks theconnecting route between the vertical power supplying mesh 220 and thepower supplying meshes 110/120 below. The position and the width for thehorizontal power supplying mesh 210 suffer a lot of limitations tocomplete the above mentioned coupling mechanism. For example, if thehorizontal power supplying mesh 210 is too wide and is not positionedsuitably, the standard-cell power supplying meshes 110, 120 of differentelectrical properties can be shadowed simultaneously. Then, thestandard-cell power supplying meshes 110, 120 cannot directly acquirethe voltage V_(DD) and the ground voltage V_(SS) simultaneously throughthe horizontal power supplying mesh 210 or the vertical power supplyingmesh 220 above. As above mentioned, the position and the width for thehorizontal power supplying mesh 210 must be properly designed to avoidthe above mentioned problems. However, such an approach reduces theflexibility of the routing and the routing design becomes much morecomplicated.

Therefore, those who are skilled in the art must develop new routingrules and layout methods to solve the above mentioned problems.

BRIEF SUMMARY OF THE INVENTION

Therefore, one object of the invention is to provide a routing rule ofthe APR tool and the related integrated circuit layout method formanaging a new type of standard-cell power supplying mesh and solvingthe problems in the prior art.

A power mesh managing method applicable in an integrated circuit isprovided. The integrated circuit comprises at least a standard cell anda standard-cell power supplying mesh of the standard cell. Thestandard-cell power supplying mesh corresponding to a first directioncouples to the standard cell. The power mesh managing method comprisesdefining a power supplying network and defining an assistant connectingnetwork on a third metal layer. The power supplying network includes aplurality of first power supplying meshes growing along the firstdirection and a plurality of second power supplying meshes growing alonga second direction. The first power supplying meshes are on a firstmetal layer and the second power supplying meshes are on a second metallayer. The assistant connecting network includes a plurality ofassistant connecting lines growing along the second direction. Thesecond metal layer is above the first metal layer and the third metallayer is below the first metal layer.

An integrated circuit comprises a standard cell, a standard-cell powersupplying mesh, a power supplying network, and an assistant connectingnetwork. The standard-cell power supplying mesh corresponding to a firstdirection couples to the standard cell. The power supplying networkincludes a plurality of first power supplying meshes corresponding tothe first direction and a plurality of second power supplying meshescorresponding to a second direction. The assistant connecting network isformed on a third metal layer. The first power supplying meshes areformed on a first metal layer and the second power supplying meshes areformed on a second metal layer. The assistant connecting networkincludes a plurality of assistant connecting lines corresponding to thesecond direction. The second metal layer is above the first metal layerand the third metal layer is below the first metal layer.

A better circuit routing method can be managed according to theinvention and the method can be implemented in the APR tool to design abetter circuit layout that avoids blocking the vias/via plugs by thepower supplying mesh below and eliminates the limitations of theposition and the width for the horizontal power supplying mesh. Not onlythe routing design flexibility is improved but also the routing designcan be done by following the well-defined rules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a three-dimensional schematic diagram illustrating thestandard cell and the standard cell power supplying meshes managed bythe APR tool according to the prior art;

FIG. 2 shows a three-dimensional schematic diagram illustrating thestandard cell, the standard-cell power supplying meshes, and the powersupplying mesh located in the layer above the standard cell in FIG. 1;

FIG. 3 shows a schematic diagram illustrating a side view of FIG. 2;

FIG. 4 shows a schematic diagram illustrating the power supplyingnetwork and the assistant connecting network located in the layer abovethe standard cell according to one embodiment of the invention;

FIG. 5 shows a schematic diagram illustrating a side view of FIG. 4; and

FIG. 6 shows the flow chart of the steps executed by the APR toolaccording to one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Now, please refer to FIG. 4 which shows a schematic diagram illustratingthe power supplying network 200 and the assistant connecting network 400located in the layer above the standard cell 100 according to oneembodiment of the invention. The structure and the functionalities ofthe standard cell 100 and the standard-cell power supplying meshes 110,120 in FIG. 4 are the same as those of the standard cell 100 and thestandard-cell power supplying meshes 110, 120 in FIG. 1. Please notethat only three rows of standard cell 100 are shown in FIG. 4, forclarity. However, there can be more standard cells 100 in the actualchip.

Please note that an assistant connecting network 400 is also located,together with the power supplying network 200, in the layer above thestandard cell 100 according to one embodiment of the invention.Similarly, the power supplying network 200 is the same as the powersupplying network 200 in FIG. 2 and includes the horizontal powersupplying mesh 210 and the vertical power supplying mesh 220. Thevias/via plugs 231/232 couple the horizontal power supplying mesh 210and the vertical power supplying mesh 220. In order to clearly mark theelectrical property, as shown in FIG. 4, the via/via plug 231 is used tocouple various power lines (that is, the voltage corresponds to theV_(DD)). The via/via plug 232 is used to couple various ground lines(that is, the voltage corresponds to the V_(SS)).

As mentioned before, if there is only the power supplying network 200located in the layer above the standard cell 100, the horizontal powersupplying mesh 210 may block the electrical coupling between thevertical power supplying mesh 220 and the standard-cell power supplyingmeshes 110, 120 (that is, limiting the via positions between thevertical power supplying mesh 220 and the standard-cell power supplyingmeshes 110, 120). Positioning the horizontal power supplying mesh 210 isalso limited. Therefore, besides the power supplying network 200, alayer of assistant connecting network 400 is set up between the powersupplying network 200 and the standard-cell power supplying meshes 110,120 to assist the electrical coupling between the power supplyingnetwork 200 and the standard-cell power supplying meshes 110, 120according to one embodiment of the invention. According to oneembodiment of the invention, the assistant connecting network 400couples to the horizontal power supplying mesh 210 through the vias/viaplugs 231/232. The assistant connecting network 400 includes a pluralityof assistant connecting lines 410 growing vertically like the verticalpower supplying mesh 220.

Thus, the horizontal power supplying mesh 210 can be successfullycoupled to the standard-cell power supplying meshes 110/120 below by wayof the assistant connecting lines 410 of the assistant connectingnetwork 400. As shown in FIG. 4, the assistant connecting lines 410couple to the standard-cell power supplying meshes 110/120 by way of thevias/via plugs 231/232, separately, according to one embodiment of theinvention. Since the assistant connecting line 410 growing verticallylike the vertical power supplying mesh 220 is vertical to thestandard-cell power supplying meshes 110/120 growing horizontally andnothing is in between to block each other, the assistant connecting line410 couples to the standard-cell power supplying meshes 110/120 by thevia/via plug 231/232 smoothly. The assistant connecting line 410 alsocouples to the horizontal power supplying mesh 210 by the via/via plug231/232. Therefore, the horizontal power supplying mesh 210 couples tothe standard-cell power supplying meshes 110/120 for conducting theexternal power into the standard cell 100.

Since the horizontal power supplying mesh 210 couples to the verticalpower supplying mesh 220 and even if the assistant connecting line 410does not couple to the vertical power supplying mesh 220 directly, thevertical power supplying mesh 220 still couples to the standard-cellpower supplying meshes 110/120 below through the horizontal powersupplying mesh 210 and the assistant connecting line 410.

Or, the assistant connecting line 410 can be coupled to the verticalpower supplying mesh 220 by the via/via plug 231/232 according toanother embodiment of the invention (not shown in the figure). Then, thevertical power supplying mesh 220 couples to the standard-cell powersupplying meshes 110/120 directly by way of the assistant connectingline 410.

Now, please refer to FIG. 5 which shows a schematic diagram illustratinga side view of FIG. 4. It is clearly shown in FIG. 5 that the verticalpower supplying mesh 220 couples to the standard-cell power supplyingmeshes 110/120 below through the horizontal power supplying mesh 210 andthe assistant connecting line 410 by way of the vias/via plugs 231/232.

Furthermore, it should be noted that the above mentioned structure canbe implemented easily by those who are skilled in the art. Since thereare usually more than three metal layers above the standard cell 100 inthe advanced process, those who are skilled in the art can select anythree metal layers to implement the above mentioned power supplyingnetwork 200 and the above mentioned assistant connecting network 400according to different requirements. For example, as the standard-cellpower supplying meshes 110, 120 are usually located at the metal layerM1, those who are skilled in the art can choose the metal layers M4, M5,M6 to implement the power supplying network 200 and the above mentionedassistant connecting network 400.

Please note that, in order to reduce the routing resource used by thenewly introduced assistant connecting network 400, the width for theassistant connecting line 410 is substantially equal to the width of avia plug according to one embodiment of the invention. Thus, such adesign releases the space of the lower metal layers. As the space of thelower metal layers is more precious, the released space can be used forrouting and coupling in the other portion of the circuit. Therefore, thebenefit of implementing the assistant connecting line 410 with lesswidth in the lower metal layers (such as the above mentioned metal layerM4) is to release more space of the lower metal layers.

Since both of the horizontal power supplying mesh 210 and the verticalpower supplying mesh 220 couple to the standard-cell power supplyingmeshes 110, 120 below by way of the assistant connecting network 400,the position and the width for the horizontal power supplying mesh 210do not suffer the same limitation mentioned before. For example, thehorizontal power supplying mesh 210 couples to the standard-cell powersupplying meshes 110, 120 by way of the assistant connecting network400. Then, even if the width for the horizontal power supplying mesh 210is larger to shadow the standard-cell power supplying meshes 110, 120below, such mechanism will not influence the electrical properties ofthe standard-cell power supplying meshes 110, 120 (that is, thestandard-cell power supplying meshes 110, 120 can acquire the voltageV_(DD) and the ground potential V_(SS) from the assistant connectingnetwork 400 above directly through the via).

Those who are skilled in the art should be able to implement thedescriptions up to now in the APR tool to set up a new routing rule.Please refer to FIG. 6 which shows the flow chart of the managing methodexecuted by the APR tool according to one embodiment of the invention.The method comprises the following steps:

Step 600: defining a standard cell 100 and related power supplyingmeshes 110, 120;

Step 610: defining a power supplying network in the layer above thestandard cell 100 where the power supplying network includes a pluralityof power supplying mesh structure 210 growing along the verticaldirection and a plurality of power supplying mesh structure 220 growingalong the horizontal direction and the power supplying mesh structure210 and the power supplying mesh structure 220 are placed on differentmetal layers;

Step 620: defining an assistant connecting network 400 between the powersupplying meshes 110, 120 of the standard cell 100 and the abovementioned power supplying network, where the assistant connectingnetwork 400 includes a plurality of connecting lines 410 growing alongthe horizontal direction;

Step 630: performing the electrical coupling for the assistantconnecting network and the power supplying mesh and performing theelectrical coupling for the assistant connecting network and the powersupplying network. The coupling step is to form the vias and the viaplugs in the vertically intersected overlapping areas of the powersupplying network and the assistant connecting network, and in thevertically intersected overlapping areas of the assistant connectingnetwork and the power supplying network.

First of all, a common standard cell, the standard-cell power supplyingmesh (Step 610), and the power supplying network (Step 620) are drawnaccording to the prior art. Then, the assistant connecting networkdisclosed before is drawn between the power supplying network and thestandard-cell power supplying mesh (Step 630). Lastly, the standard-cellpower supplying mesh, the power supplying network, and the assistantconnecting network are coupled by way of the vias (Step 640). Those whoare skilled in the art should be able to understand the description upto now. Thus, the details of the program codes of the APR tool will notbe repeated hereinafter.

Please note that, as one additional metal layer is used to manage theassistant connecting network according to one embodiment of theinvention, the assistant connecting network is only implemented abovethe standard cell. The assistant connecting network is not arrangedabove the more complicated macro block. However, such an example is onlyone embodiment of the invention and should not be construed as anylimitation on the implementation of the invention.

Compared to the prior art, a better circuit routing method can bemanaged according to the invention. The method can be implemented in theAPR tool to design a better circuit layout that avoids blocking the viasby the power supplying mesh below. The limitations of the position andthe width for the horizontal power supplying mesh can be eliminated. Notonly the flexibility of the routing design is improved but also therouting design can be done by following the well-defined rules.

Although the description of the invention is by way of above-mentionedexamples of embodiments, however, it should not be construed as anylimitation on the scope of the invention. Various modifications orchanges can be performed by those who are skilled in the art withoutdeviating from the scope of the invention.

1-20. (canceled)
 21. A power mesh managing method, applicable in an integrated circuit, that comprises at least one standard cell and a standard-cell power supplying mesh of the standard cell where the standard-cell power supplying mesh couples to the standard cell, the power mesh managing method comprising: defining a power supplying network, for supplying power to the standard cell, including a plurality of first power supplying meshes growing along a first direction and a plurality of second power meshes growing along a second direction wherein the plurality of first power supplying meshes are formed on a first metal layer and the plurality of second power supplying meshes are on a second metal layer; and defining an assistant connecting network on a third metal layer, wherein the assistant connecting network includes a plurality of assistant connecting lines growing along the second direction and, wherein the plurality of assistant connecting lines are directly connected to the second metal layer by via holes, and wherein the width of each assistant connecting line of the assistant connecting network is smaller than the width of each mesh line of the power supplying network; wherein the second metal layer is above the first metal layer and the third metal layer is below the first metal layer.
 22. The power mesh managing method according to claim 21, further comprising: coupling the power supplying network to an external power and the standard-cell power mesh for inputting the external power to the standard cell through the power supplying network and the standard-cell power supplying mesh.
 23. The power mesh managing method according to claim 22, further comprising: coupling the plurality of assistant connecting lines to the standard-cell power supplying mesh and the power supplying network.
 24. The power mesh managing method according to claim 23, wherein the step of coupling the plurality of assistant connecting lines to the power supplying network comprises: coupling the plurality of assistant connecting lines to the plurality of first power supplying meshes.
 25. The power mesh managing method according to claim 23, wherein the step of coupling the plurality of assistant connecting lines to the power supplying network comprises: coupling the plurality of assistant connecting lines to the plurality of second power supplying meshes.
 26. The power mesh managing method according to claim 22, wherein the step of coupling the plurality of assistant connecting lines to the standard-cell power supplying mesh comprises: coupling the plurality of assistant connecting lines to the standard-cell power supplying mesh by via holes.
 27. The power mesh managing method according to claim 26, wherein the width of each assistant connecting line for the plurality of assistant connecting lines is substantially equal to the width of the via hole.
 28. The power mesh managing method according to claim 21, further comprising: coupling the plurality of first power supplying meshes to the plurality of second power supplying meshes.
 29. An integrated circuit, comprising: a standard cell; a standard-cell power supplying mesh coupling to the standard cell; a power supplying network, for supplying power to the standard cell, including a plurality of first power supplying meshes corresponding to a first direction and a plurality of second power supplying meshes corresponding to a second direction, wherein the plurality of first power supplying meshes are formed on a first metal layer and the plurality of second power supplying meshes are on a second metal layer; and an assistant connecting network formed on a third metal layer, wherein the assistant connecting network includes a plurality of assistant connecting lines corresponding to the second direction and, wherein the plurality of assistant connecting lines are directly connected to the second metal layer by via holes, and wherein the width of each assistant connecting line of the assistant connecting network is smaller than the width of each mesh line of the power supplying network; wherein the second metal layer is above the first metal layer and the third metal layer is below the first metal layer.
 30. The integrated circuit according to claim 29, wherein the power supplying network couples to an external power and the standard-cell power supplying mesh for inputting the external power to the standard cell through the power supplying network and the standard-cell power supplying mesh.
 31. The integrated circuit according to claim 30, wherein the plurality of assistant connecting lines couple to the standard-cell power supplying mesh and the power supplying network.
 32. The integrated circuit according to claim 31, wherein the plurality of assistant connecting lines couple to the plurality of second power supplying meshes.
 33. The integrated circuit according to claim 31, wherein the plurality of assistant connecting lines couple to the plurality of first power supplying meshes.
 34. The integrated circuit according to claim 31, wherein the plurality of assistant connecting lines couple to the standard-cell power supplying mesh by via holes.
 35. The integrated circuit according to claim 34, wherein the width of each assistant connecting line for the plurality of assistant connecting lines is substantially equal to the width of the via hole.
 36. The integrated circuit according to claim 29, wherein the plurality of first power supplying meshes couple to the plurality of second power supplying meshes. 